Apparatus and method for plasma etching

ABSTRACT

A plasma etching method for a plasma etching apparatus including: a processing chamber for performing plasma etching on an object to be processed; a first gas supply source; a second gas supply source; a first gas inlet for introducing a processing gas into the processing chamber; a second gas inlet for introducing a processing gas into the processing chamber; a flow rate regulator for regulating the flow rate of the processing gas; and a gas shunt for dividing the first processing gas into a plurality of portions, wherein the second processing gas is merged with at least one part between the gas shunt and the first gas inlet and between the gas shunt and the second gas inlet.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. application Ser. No. 10/793,886, filed Mar.8, 2004 now abandoned. This application relates to and claims priorityfrom Japanese Patent Application No. 2003-206042, filed on Aug. 5, 2003.The entirety of the contents and subject matter of all of the above isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma etching apparatus forprocessing an object to be processed such as a semiconductor wafer, anda plasma etching method using the plasma etching apparatus.

2. Description of the Related Art

In a semiconductor chip manufacturing process, a plasma etchingapparatus using reactive plasma to process an object to be processedsuch as a semiconductor wafer is conventionally used.

Here, with reference to a cross-sectional view of an object to beprocessed shown in FIG. 13, etching for forming a poly-silicon (Poly-Si)gate electrode of an MOS (Metal Oxide Semiconductor) transistor(hereinafter referred to as “gate etching”) will be explained as oneexample of a plasma etching process. As shown in FIG. 13( a), an objectto be processed 1 prior to etching is formed of a silicon dioxide (SiO₂)film 3, poly-silicon film 4 and photoresist mask 5 deposited on thesurface of a silicon (Si) substrate 2 in the named order. Thisphotoresist mask 5 is formed via a photolithography process by applyinga photoresist, projecting the same pattern onto one or a plurality ofchips for exposure to light using a mask called a “reticule” through areduced projection photolithography apparatus, and developing the same.The dimension of this photoresist mask 5, that is, a photoresist maskwidth 7, greatly affects the width of a gate electrode which will bedescribed later, and is therefore subject to strict control.

Gate etching is a process for removing the poly-silicon film 4 in anarea not covered with the photoresist mask 5 by exposing the object tobe processed 1 to reactive plasma, and by this process, a gate electrode6 is formed as shown in FIG. 13( b). Since a gate width 8 at the bottomof the gate electrode 6 greatly affects the performance of theelectronic device, it is subject to strict control as most important CD(critical dimension). For this reason, a target completion dimension ispreset for the gate width 8.

Furthermore, a value obtained by subtracting the gate width 8 afteretching from the photoresist mask width 7 before etching is called a “CDshift”, and constitutes an important index for expressing the quality ofgate etching.

A conventional example of a plasma etching apparatus which carries outthe above described gate etching will be explained with reference toFIG. 14. A processing chamber cover 12 is placed on a quasi-cylindricalprocessing chamber side wall 11, and a processing chamber 13 defined bythe above parts is provided with a substrate holder 14.

A processing gas 21 is introduced into the processing chamber 13 throughan inlet 22 provided in the central part of the processing chamber cover12 to generate plasma 25. Plasma etching is performed by exposing theobject to be processed 1 to this plasma 25. The processing gas 21 and avolatile substance generated by the reaction in the plasma etchingprocessing are exhausted from the outlet 30. A vacuum pump (not shownhere) is connected to the tip of the outlet 30 and the pressure in theprocessing chamber 13 is thereby reduced to approximately 1 Pa (Pascal).

Gate etching is performed using the plasma etching apparatus asdescribed above, but with the recent increase in the diameter of theobject to be processed 1, it is becoming more difficult to secure thein-plane uniformity of etching rates or the in-plane uniformity of thegate width 8 over a wide area of the object to be processed 1. Likewise,along with the recent miniaturization of semiconductor devices, demandsare increasing for more severe dimensional control of the gate width 8.

Next, adhesion and deposition of reaction products onto the side of agate electrode, which is one of influences on the dimension of the gatewidth 8, will be explained. A plurality of gases such as chlorine (Cl₂),hydrogen bromide (HBr) and oxygen (O₂) are conventionally used forprocessing of gate etching. During etching, these gases are in a plasmastate to perform etching on the poly-silicon film 4, but during theprocess, chlorine, hydrogen bromide and oxygen contained in theprocessing gas 21 are dissociated, and the thus-produced ions andradicals of Cl (chlorine), H (hydrogen), Br (bromine) and O (oxygen)react with silicon deriving from the poly-silicon film 4, producingreaction products. Of these reaction products, volatile ones areexhausted from the outlet 30, but non-volatile products are adhered ordeposited onto the inner side (vacuum side) of the processing chamberside wall 11, the processing chamber cover 12 and the sides of thepoly-silicon film 4 and photoresist mask 5. When the reaction productsare deposited on the sides of the poly-silicon film 4 and photoresistmask 5, they serve as a mask for etching, which often increases the gatewidth 8.

Especially when a compound SiBr_(x) (x=1, 2, 3) of silicon and bromineor compound SiCl_(x) (x=1, 2, 3) of silicon and chlorine reacts withoxygen (O), Si_(x)Br_(y)O_(z) (x, y, z: natural number) orSi_(x)Cl_(y)O_(z) (x, y, z: natural number) which are non-volatile andhave high deposition characteristic is produced, and adhesion ordeposition of these products to the poly-silicon film 4 and photoresistfilm 5 may cause an increase of the gate width 8.

The increase of the gate width 8 may occur nonuniformly within the planeof the object to be processed 1. That is, nonuniform CD shifts may occurwithin the plane of the object to be processed 1. For example, in anarea with a high etching rate, the concentration of reaction productsincluding silicon deriving from the poly-silicon film 4 becomes higherthan in areas with a low etching rate, which may cause in-planenonuniformity of CD shifts.

Furthermore, in the central part of the object to be processed 1, allsurrounding areas are subject to etching, whereas outside the outermostregion of the wafer, there is no area subject to etching. For thisreason, even if an etching rate is uniform within the plane of theobject to be processed 1, the concentration of reaction productsincluding silicon deriving from the poly-silicon film 4 is high in thecenter portion and low in the outer regions. This may also causein-plane nonuniformity of CD shifts.

Furthermore, as described above, reaction products are deposited on theprocessing chamber side wall 11 or inner side (vacuum side) of theprocessing chamber cover 12 through plasma etching processing, butduring plasma etching, radicals and ions of chlorine, hydrogen, bromine,oxygen and these compounds may be dissociated from these depositions anddischarged into the plasma 25. In this case, the concentration of theradicals and ions discharged from the reaction products is likely toincrease in the outer regions of the object to be processed 1. This isbecause the processing chamber cover 12 is placed parallel to the objectto be processed 1 as shown in FIG. 14, and radicals and ions dischargedfrom the deposited reaction products are likely to disperse over thewhole object to be processed 1, while the processing chamber side wall11 is located to surround the outer regions of the object to beprocessed 1 and radicals and ions discharged from the reaction productsdeposited thereto are likely to cause an increase of concentration inthe outer regions of the object to be processed 1. The radicals and ionsdischarged from the reaction products as described above may causedeterioration of in-plane uniformity of CD shifts on the surface of theobject to be processed 1.

As described above, nonuniformity of concentration of reaction productsis caused on locations within the plane of the object to be processed 1,but this nonuniformity varies from moment to moment according to thecondition in the processing chamber 13. That is, even if the totalamount and composition of the processing gas 21 or process inputconditions such as the pressure in the processing chamber 13 are thesame when plasma etching is performed, CD shifts fluctuate. This isbecause the adhesion condition of reaction products deposited on theprocessing chamber cover 12 and processing chamber side wall 11 variesfrom moment to moment as the plasma etching processing advances asdescribed above.

In addition to the advance of the above described plasma etchingprocessing, the condition in the processing chamber also changes througha process called “cleaning.” Every time the aforementioned plasmaetching process is carried out, the amount of reaction productsdeposited on the inner side (vacuum side) of the processing chamber sidewall 11 and the processing chamber cover 12 increases. When thesedepositions fall off and attach to the surface of the object to beprocessed 1, the yield of volume production of semiconductor devices isdeteriorated. To prevent this, plasma cleaning using reactive plasma iscarried out periodically to remove the aforementioned depositions.Furthermore, depositions which cannot be removed by plasma cleaning areremoved by operations called “wet cleaning” or “manual cleaning” whichare manually performed by the operator with the processing chamber 13left open to the atmosphere. These two types of cleaning processesreduce the amount of depositions stuck to the processing chamber cover12 and processing chamber side wall 11. As shown above, since thecondition in the processing chamber 13 varies from moment to moment,distributions of radicals and ions on the surface of the object to beprocessed 1 also change accordingly.

In the plasma etching apparatus of the conventional example (prior art)shown in FIG. 14, the processing gas is only introduced from the inlet22 provided above the central part of the object to be processed 1, andtherefore the concentration of radicals of gas components contained inthe processing gas or ions resulting from dissociation is often high inthe central part and low in the outer regions of the object to beprocessed 1.

One art intended to improve in-plane uniformity of ions and radicals inplasma is an art of introducing a processing gas from a plurality ofparts of the processing chamber. This art relates to a reactive ionsetching apparatus provided with a flow rate controller capable ofintroducing the processing gas into the processing chamber through aplurality of inlets and controlling the flow rate of the processing gasfor each inlet independently (e.g., see Patent Document 1). This art iscapable of changing the in-plane uniformity of the etching rate, butsince the processing gas introduced from the respective inlets has thesame composition, it cannot sufficiently adjust the in-plane uniformityof ions and radicals.

There is another art of introducing a reaction product gas into theprocessing chamber for the purpose of improving the concentrationdistribution of reaction products on the surface of the object to beprocessed 1. This art relates to a method of dry etching which providestwo gas inlets, introduces a reactive gas from one inlet and introducesa reaction product gas generated by an etching reaction from the otherinlet as a reaction inhibition gas for the purpose of equalizing theetching rate on an object to be processed (e.g., see Patent Document 2).The use of this method can adjust the in-plane uniformity of ions andradicals and improve in-plane uniformity of the etching rate.

However, since the position of introducing the reaction product gas asthe reaction inhibition gas is limited to one inlet, this structure hasconstraints on the improvement of in-plane uniformity of the etchingrate. For example, when the etching rate in the central part of theobject to be processed is greater than the etching rate in the outerregions, it is possible to improve the in-plane uniformity of theetching rate by introducing a reaction product gas into the central partas the reaction inhibition gas. However, on the contrary, when theetching rate in the outer regions of the object to be processed isgreater than the etching rate in the central part, this structurerequires gas pipes to be replaced, so it is unable to respond to thedemand quickly. It also has the disadvantage that a supply source of thereaction product gas and piping system need to be added in addition tothe gas used for normal etching to the apparatus.

In view of the above described problems, it is an object of the presentinvention to provide a plasma etching apparatus and plasma etchingmethod capable of carrying out processing with excellent in-planeuniformity on an object to be processed having a large diameter.

[Patent Document 1]

Japanese Patent Application Laid-Open No. 62-290885

[Patent Document 2]

Japanese Patent Application Laid-Open No. 5-190506

[Patent Document 3]

Specification of U.S. Pat. No. 6,418,954

BRIEF SUMMARY OF THE INVENTION

In order to solve the problems of the above described prior arts, thepresent invention provides a plurality of inlets 65 for introducing aprocessing gas 21 into a processing chamber 13 and uses the respectiveinlets 22 to adjust the flow rate or composition of the processing gas21. The processing gas (first processing gas) from a common gas systemat that time is divided into a plurality of portions, a gas from anadditional gas system (second processing gas) is mixed with therespective piping systems after the division to thereby adjust thecomposition and/or flow rate of the processing gas introduced from theplurality of inlets provided in the processing chamber 13.

Furthermore, the present invention measures the size of a photoresistmask width 7 formed in a photolithography process before plasma etchingand makes an analysis using the measurement result to thereby adjust thecomposition and/or flow rate of the processing gas 21 introduced throughthe plurality of inlets.

Furthermore, the present invention measures the gate width 8 afteretching and makes an analysis using the measurement result to therebyadjust the composition and/or flow rate of the processing gas 21introduced through the plurality of inlets.

Furthermore, the present invention calculates the amount of depositionin the processing chamber 13 from the photoreception result of plasmaemission, estimates the amount of generated ions and radicals from thecalculation result to thereby adjust the composition and/or flow rate ofthe processing gas 21 introduced from the plurality of inlets.

Furthermore, the present invention provides a plurality of plasmaemission photoreception sections above the object to be processed 1,calculates distributions of ions and radicals from the plasmaphotoreception result and adjusts the composition and/or flow rate ofthe processing gas 21 introduced from the plurality of inlets using theresult.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a gas piping system of a first embodiment of thepresent invention;

FIG. 2 is a top view of a processing chamber cover used in the firstembodiment of the present invention;

FIG. 3 is a sectional side view of a processing chamber used for thefirst embodiment of the present invention;

FIG. 4 is a table showing a set flow rate of the processing gas used inthe first embodiment of the present invention and flow rate of each gas;

FIG. 5 is a graph showing an oxygen concentration distribution and atable showing a gate width, which shows a comparison between resultsobtained from the first embodiment of the present invention and resultsobtained from the conventional example;

FIG. 6 illustrates the gas system of the first embodiment of the presentinvention, which shows a structure different from that in FIG. 1;

FIG. 7 is a sectional side view of a processing chamber used in a secondembodiment of the present invention;

FIG. 8 is a top view of a showerhead plate used for the secondembodiment of the present invention;

FIG. 9 illustrates a gas piping system and control system according to athird embodiment of the present invention;

FIG. 10 is a sectional side view of an object to be processed before andafter etching of the third embodiment of the present invention;

FIG. 11 illustrates a gas piping system and control system according toa fourth embodiment of the present invention;

FIG. 12 illustrates a gas piping system and control system according toa fifth embodiment of the present invention;

FIG. 13 is a sectional side view of an object to be processed before andafter gate etching processing; and

FIG. 14 is a sectional side view of a processing chamber showing aconventional example of a plasma etching apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

With reference to FIG. 1 through FIG. 6, a first embodiment of thepresent invention will be described in detail below. FIG. 1 illustratesa gas piping system of a plasma etching apparatus to which the firstembodiment of the present invention is applied.

Furthermore, a top view of a processing chamber cover 12 in thisembodiment is shown in FIG. 2. As shown in FIG. 2, a first gas inlet65-1 is set in the center portion of the processing chamber cover 12 andeight second gas inlets 65-2 are set in a circular form around the firstgas inlet 65-1.

As shown in FIG. 1, this plasma etching apparatus is constructed of aprocessing chamber 13 having a processing chamber cover 12, a substrateholder 14 provided in the processing chamber, a first gas inlet 65-1 andsecond gas inlets 65-2 provided in the processing chamber cover 12, acommon gas system 40 which is a first processing gas supply source, anadditional gas system 50 which is a second processing gas supply source,a shunt 60 which shunts a first processing gas from the common gassystem 40 into a plurality of parts, a merging section 63-1 provided ata position of a pipe between a first shunt outlet 62-1 of the shunt 60and the first gas inlet 65-1 for merging a second processing gas and amerging section 63-2 provided at a position of a pipe between a secondshunt outlet 62-2 of the shunt 60 and the second gas inlet 65-2 formerging the second processing gas.

The common gas system 40 is constructed of gas cylinders 41-1 and 41-2as gas supply sources, flow rate regulators 42-1 and 42-2 which regulatethe flow rates of the respective gases, valves 43-1 and 43-2 which letpass or stop the respective gases and a merging section 44 which mergesthe respective gases of the common gas system 40.

In this embodiment, the gas cylinder 41-1 is filled with hydrogenbromide (HBr) and the gas cylinder 41-2 is filled with chlorine (Cl₂) ascommon gases.

The common gases which have merged at the merging section 44 are guidedto the gas shunt 60 located downstream. The gas shunt 60 is a devicehaving the function of shunting an arbitrary gas which has entered a gasshunt inlet 61 into a plurality of shunt outlets at an arbitrary flowrate ratio. This gas shunt 60 shunts a processing gas into two shuntoutlets, and one shunt outlet thereof is provided with a flow meterwhich measures the flow rate of the processing gas and a restrictorwhich restricts or regulates the flow of the processing gas, and theother shunt outlet is provided with a mass flow controller which can letflow the processing gas at a set flow rate. A flow rate set value issent from this flow meter to a mass flow controller, which makes itpossible to shunt the processing gas entering the inlet into two shuntoutlets at an arbitrary flow rate ratio (e.g., see Patent Document 3).

In this embodiment, a mixed gas of hydrogen bromide and chlorine isshunt into two outlets by this gas shunt 60; shunt outlet 62-1 and shuntoutlet 62-2, at a flow rate ratio of 8:2.

The additional gas system 50 is constructed of a gas cylinder 51 as agas supply source, a branch 52 for branching the gas into pluralportions (2 portions in this embodiment), flow rate regulators 53-1 and53-2 which regulate the flow rates of the respective gases, and valves54-1 and 54-2 for letting flow or stopping the gas. In this embodiment,oxygen (O₂) is put in a gas cylinder 51 as an additional gas.

The common gas (a mixed gas of hydrogen bromide and chlorine in thisembodiment) output from the shunt outlet 62-1 merges with the additionalgas (oxygen in this embodiment) which has passed through the valve 54-1at the merging section 63-1, and the mixed gas of common gas andadditional gas is guided to the first gas inlet 65-1 provided in thecenter of the processing chamber cover 12.

Likewise, the common gas (a mixed gas of hydrogen bromide and chlorinein this embodiment) output from the shunt outlet 62-2 merges with theadditional gas (oxygen in this embodiment) which has passed through thevalve 54-2 at the merging section 63-2, and the mixed gas of common gasand additional gas is guided to the second gas inlets 65-2 provided inthe outer regions of the processing chamber cover 12.

Using the above described structure and by regulating the set flow ratesof the flow rate regulators 42-1, 42-2, 53-1 and 53-2 and the flow rateratio between the shunt outlet 62-1 and shunt outlet 62-2 of the shunt60, processing gases having different flow rates and compositions areintroduced through the first gas inlet 65-1 and second gas inlets 65-2.

Then, the plasma etching apparatus of this embodiment will be explainedwith reference to FIG. 3. The processing chamber cover 12 is placed onthe processing chamber side wall 11 and in the processing chamber 13formed of these parts, the substrate holder 14 is placed. A circulargroove is formed in the top end face of the processing chamber side wall11 and an O-ring 15 is filled in this groove. This O-ring 15 keeps theprocessing chamber 13 airtight.

A chucking electrode 16 is buried in the substrate holder 14, and anelectrostatic force is produced between the chucking electrode 16 andobject to be processed 1 by a DC power supply 17 connected to thechucking electrode 16, whereby the object to be processed 1 is attractedto the substrate holder 14. Furthermore, a switch 18 is provided betweenthe chucking electrode 16 and DC power supply 17 for turning ON/OFF a DCvoltage to be applied.

The processing gas 21-1 which has passed through the merging section63-1 and the processing gas 21-2 which has passed through the mergingsection 63-2 are introduced into the processing chamber 13 through thefirst inlet 65-1 and the second inlets 65-2, respectively. These firstinlet 65-1 and second inlets 65-2 are formed of pipes penetrating theprocessing chamber cover 12. High-frequency coils 23 are placed on theprocessing chamber cover 12 and when a high-frequency power supply 24applies high frequency to the high-frequency coils 23, the processinggas 21 is transformed into plasma 25. A switch 26 is provided betweenthe high-frequency coils 23 and high-frequency power supply 24 forturning ON/OFF a high-frequency voltage to be applied.

Plasma etching process is performed by exposing the object to beprocessed 1 to the plasma 25. A high-frequency application electrode 27for applying a high-frequency voltage is buried in the substrate holder14, and when the high-frequency voltage is applied by a high-frequencypower supply 28 connected thereto, the high-frequency applicationelectrode 27 produces a bias potential, attracts ions produced in theplasma 25 into the object to be processed 1 and performs anisotropicetching. A switch 29 is provided between the high-frequency applicationelectrode 27 and the high-frequency power supply 28 for turning ON/OFFthe high-frequency voltage to be applied.

The processing gas 21 and volatile substances produced by a reaction inthe plasma etching processing are exhausted through an outlet 30. Avacuum pump (not shown here) is connected to the tip of the outlet 30 toreduce the pressure in the processing chamber 13 to approximately 1 Pa(Pascal). Furthermore, a pressure regulating valve 31 is providedbetween the outlet 30 and the vacuum pump to regulate the pressure inthe processing chamber 13 by regulating the opening of the pressureregulating valve 31.

Here, set flow rates of the respective processing gases and the numbersof flow rate regulators which regulate the respective flow rates used inthe conventional example and this embodiment are shown in FIG. 4( a),and the flow rate ratio of the gas shunt 60 and the flow rates of theprocessing gases introduced through first inlet 65-1 and second inlets65-2 are shown in FIG. 4( b). In FIG. 4( b), when the shunt ratio of thegas shunt 60, that is, the ratio of the flow rate from the shunt outlet62-1 to the flow rate from the shunt outlets 62-2 is 100:0 and the setflow rate of the flow rate regulator 53-2 is 0 sccm, the processing gasis introduced only through the gas inlet 65-1 placed in the center ofthe processing chamber cover 12, which is equivalent to the processingin the conventional example, and therefore described as the conventionalexample.

In the case of the condition shown in FIG. 4, while the flow rate ratioof hydrogen bromide, chlorine and oxygen of the processing gasintroduced through the first inlet 65-1 in the conventional example andthis embodiment is 20:10:1, the flow rate ratio of hydrogen bromide,chlorine and oxygen of the processing gas introduced through the secondinlets 65-2 of this embodiment is 20:10:2. That is, in this embodiment,the processing gas of higher oxygen concentration is introduced throughthe second inlets 65-2 than through the first inlet 65-1.

Next, FIG. 5( a) shows a comparison of the oxygen concentrationdistribution on the surface of the object to be processed 1 having adiameter of 300 mm between the conventional example and the presentembodiment. As opposed to the conventional example where the oxygenconcentration is lower in the outer regions than in the center portionof the object to be processed, it is evident in this embodiment that thereduction of oxygen concentration in the outer regions is suppressed andthat the in-plane uniformity is improved. Furthermore, FIG. 5( b) showsthe measurement result of the gate width 8 of the object to be processed1. As shown in this figure, while there is a large difference of thegate width 8 between the center portion and outer region of the priorart, the difference is reduced in this embodiment. This is because theprocessing gas of higher oxygen concentration is introduced into theouter regions than the center portion, non-volatile reaction productsSi_(x)Br_(y)O_(z) (x, y, z: natural number) or Si_(x)Cl_(y)O_(z) (x, y,z: natural number) are deposited more on the sides of the poly-siliconfilm 4 and photoresist film 5 in the outer regions than the centerportion and the gate width 8 is increased compared to the conventionalexample. Thus, by introducing processing gases having different mixingratios through a plurality of gas inlets 65, it is possible to improvethe in-plane uniformity of CD shifts of the object to be processed 1 andrealize gate etching whereby the gate width 8 becomes more uniformwithin the plane.

According further to this embodiment, when the processing gases areintroduced into a plurality of gas inlets 65 as shown in FIG. 1, acommon gas which is commonly introduced into the plurality of gas inlets65 (hydrogen bromide and chlorine in this embodiment) is shunted by thegas shunt 60 at an arbitrary flow rate ratio and the additional gases(oxygen in this embodiment) with different flow rates are introduced atplaces downstream from the respective shunt outlets 62-1 and 62-2. Thismakes it possible to introduce processing gases having different flowrates and compositions from the plurality of gas inlets 65 with a simplestructure.

This embodiment uses hydrogen bromide and chlorine as common gases, butcommon gases are not limited to them and other gases can also be used.

Furthermore, this embodiment uses oxygen as an additional gas. However,the additional gas is not limited to oxygen, and it is possible to useother gases for generating depositional reaction products as additionalgases. Furthermore, on the contrary, it is also possible to use gaseswhich inhibit the generation of depositional reaction products asadditional gases, regulate their concentration distributions within theplane of the object to be processed 1 to thereby improve the in-planeuniformity of the gate width 8.

Furthermore, this embodiment uses two types of gases of hydrogen bromideand chlorine as common gases, but common gases are not limited to these.It is also possible to use a single gas, or three or more types of gasesas the common gas.

Furthermore, this embodiment only uses oxygen as an additional gas, butthe additional gas is not limited to one type of gas, and a plurality ofgases can also be used. FIG. 6 shows an example of using a plurality ofadditional gases. In this case, it is possible to provide a firstadditional gas system 50-1 consisting of a gas cylinder 51-1 filled witha first additional gas, a branch 52-1, flow rate regulators 53-1 and53-2 and valves 54-1 and 54-2, and a second additional gas system 50-2consisting of a gas cylinder 51-2 filled with a second additional gas, abranch 52-2, flow rate regulators 53-3 and 53-4 and valves 54-3 and54-4. The common gases output from the gas shunt outlets 62-1 and 62-2are mixed with the first additional gas and second additional gas at thesections 63-1 and 63-2, respectively, and the processing gases withdifferent flow rates and compositions are introduced into the gas inlets65-1 and 65-2.

Furthermore, this embodiment uses a smaller total flow rate of theprocessing gas 21-2 introduced from the gas inlets 65-2 placed in theouter regions of the processing chamber cover 12 than a total flow rateof the processing gas 21-1 introduced from the gas inlet 65-1 placed inthe center portion, but the present invention is not limited to thisembodiment. The implementer of the present invention can freely decidethe flow rates of the processing gases introduced from the respectiveinlets to realize optimal plasma etching. Therefore, if a greater totalflow rate of the processing gas 21-2 should be introduced from the gasinlets 65-2 than a total flow rate of the processing gas 21-1 introducedfrom the gas inlet 65-1 to achieve a better etching result, such settingis also acceptable.

Furthermore, this embodiment assigns a greater value to the ratio of theoxygen flow rate to the total flow rate of the processing gas 21-2introduced through the gas inlets 65-2 than the ratio of the oxygen flowrate to the total flow rate of the processing gas 21-1 introducedthrough the gas inlet 65-1, but the present invention is not limited tothis embodiment. For example, when the gate width 8 in the outer regionsis greater than a target completion size and the gate width 8 in thecenter portion is smaller than the target product size, it is possibleto reduce the ratio of the oxygen flow rate to the total flow rate ofthe processing gas 21-2 introduced through the gas inlets 65-2 andincrease the oxygen flow rate to the total flow rate of the processinggas 21-1 introduced through the gas inlet 65-1 to thereby approximatethe gate widths 8 at the respective positions to the target completionsize.

Furthermore, this embodiment uses the gas shunt 60 described in PatentDocument 3, but the present invention is not limited to this embodiment.It is possible to use a device having a different structure to shunt theprocessing gas into a plurality of parts. Furthermore, this embodimentprovides the merging section 63-1 for merging the second processing gason the pipe between the first shunt outlet 62-1 of the shunt 60 whichshunts the first processing gas from the common gas system 40 into aplurality of portions and the first gas inlet 65-1, and the mergingsection 63-2 for merging the second processing gas on the pipe betweenthe second shunt outlet 62-2 of the shunt 60 and the second gas inlet65-2, but it is also possible to adopt a structure having at least oneof the merging sections 63-1 and 63-2 for merging the second processinggas.

Second Embodiment

Then, a second embodiment of the present invention will be explainedusing FIG. 7 and FIG. 8. While the first embodiment makes a plurality ofholes in the processing chamber cover 12 to provide the second gasinlets 65-2, this embodiment places below the processing chamber cover12 a plate called a “showerhead plate” in which a plurality of holes areformed, and forms second gas inlets 65-2 using the holes in theshowerhead plate 19 as shown in FIG. 7. Furthermore, the same pipingsystem as that explained in the first embodiment will be used tointroduce processing gases into a processing chamber 13.

A processing gas 21-1 which has passed through a merging section 63-1 isintroduced into the processing chamber 13 through a first gas inlet 65-1formed of a pipe penetrating the processing chamber cover 12 andshowerhead plate 19. On the other hand, a processing gas 21-2 which haspassed through a merging section 63-2 is introduced between theprocessing chamber cover 12 and showerhead plate 19 through a gasintroduction pipe 22 and then introduced into the processing chamber 13through second inlets 65-2 formed on the showerhead plate. Furthermore,the processing gas 21-1 introduced through the first inlet 65-1 and theprocessing gas 21-2 introduced through the gas introduction pipe 22 areprevented from mixing with each other in the space between theprocessing chamber cover 12 and the showerhead plate 19. Furthermore, anO-ring 15′ placed beneath the showerhead plate 19 maintainsairtightness.

FIG. 8 shows a top view of the showerhead plate 19. A hole for passingthrough the pipe forming the first inlet 65-1 is formed in the center ofthe showerhead plate 19, and the second gas inlets 65-2 are formed in acircular form around the first inlet 65-1.

The conductance between the processing chamber cover 12 and theshowerhead plate 19 is designed to be sufficiently larger than theconductance of each of the second gas inlets 65-2, and the processinggas 21-2 introduced through the gas introduction pipe 22 is introducedinto the processing chamber 13 from the respective second gas inlets65-2 at the same flow rate.

This embodiment makes it possible to form the second gas inlets 65-2with a simpler structure than that of the first embodiment shown in FIG.2 and FIG. 3. Moreover, using the structure explained in the firstembodiment allows effects similar to those of the first embodiment to beachieved.

Third Embodiment

Then, a third embodiment of the present invention will be explained withreference to FIG. 9. This embodiment adds a measuring instrument 70, adatabase 72, an analysis section 74 and a control section 76 to thestructure explained in the first embodiment that allows processing gaseswith different flow rates and compositions to be introduced through aplurality of gas inlets 65.

The measuring instrument 70 is intended to measure an object to beprocessed 1 before etching or after etching, and a length measuring SEM(Scanning Electron Microscope) and measuring instrument called a“CD-SEM” are examples of this measuring instrument. This irradiates thesurface of the object to be processed 1 with electron beams and acquiresinformation on projections and depressions on the surface of the objectto be processed 1 using secondary electrons emitted from the irradiatedlocations, which allows to measure a photoresist mask width 7 beforeetching and gate width 8 after etching. Moreover, in addition to this, aso-called “OCD (Optical-CD) measuring instrument” can also be used whichirradiates the surface of the object to be processed 1 with light raysand acquires information on projections and depressions on the surfaceof the object to be processed 1 using the reflected light. In addition,a so-called “AFM (Atomic Force Microscope)” can also be used as themeasuring instrument 70, which scans the surface of the object to beprocessed 1 using a lever provided with a small probe called a“cantilever” at one end and acquires information on projections anddepressions on the surface of the object to be processed 1. This OCDmeasuring instrument or AFM also allows measurement of the photoresistmask width 7 before etching and gate width 8 after etching.

Measured data 71 obtained by this measuring instrument 70 at a pluralityof positions of the object to be processed 1 is sent to and stored inthe database 72.

Data 73 stored in the database 72 is sent to the analysis section 74.The analysis section 74 carries out an analysis based on the data 73,and a control command 75 is sent to the control section 76. Based on thecontrol command 75, the control section 76 sends a control signal 77 toflow rate regulators 42-1, 42-2, 53-1, 53-2 and valves 43-1, 43-2, 54-1,54-2 and gas shunts 60 and pressure regulating valve 31. These devicesperform control based on the received control signal 77.

As described above, by adding the measuring instrument 70, database 72,analysis section 74 and control section 76 to the first embodiment, thisembodiment can cope with differences in the photoresist mask width 7between the center portion and the outer regions of the object to beprocessed 1. It can further cope with variations in the etching resultwhich varies from one etching process to another. Hereinafter, anexample of the processing method using this structure will be explainedmore specifically.

First, a case where the photoresist mask width 7 of the object to beprocessed 1 is measured before etching will be explained. Thephotoresist mask width 7 on the surface of the object to be processed 1is measured using the measuring instrument 70 such as CD-SEM, OCDmeasuring instrument or AFM first, and then the measured data 71 is sentto the database 72. This measured data 71 includes data indicatingmeasured locations in the object to be processed 1 and data of thephotoresist mask width 7 before etching. Furthermore, when a pluralityof objects to be processed are processed successively in massproduction, the measured data 71 also includes data for identifying eachof the plurality of objects to be processed.

When the photoresist mask width 7 is measured at a plurality oflocations within the plane of the object to be processed 1 and itsin-plane distribution is calculated, it is important to measure the samepositions in a plurality of chips formed on the surface of the object tobe processed 1. This is because complicated patterns are formed in achip and the photoresist mask width 7 is not always identical in allpatterns in the chip. Moreover, to suppress variations in theperformance among chips formed on the object to be processed 1, it isimportant to suppress variations in the photoresist mask width 7 at thesame position in the chip from one chip to another.

The data 73 stored in the database 72 is sent to the analysis section 74at appropriate timings. The analysis section 74 analyzes the in-planedistribution of the photoresist mask width 7 on the surface of theobject to be processed 1 based on the data 73. For example, as shown inFIG. 10, when the photoresist mask width 7-1 of a chip in the centerportion of the object to be processed 1 is large, while the photoresistmask width 7-2 of a chip in the outer region is small, it is possible toregulate the gas condition so that the CD shift becomes greater in thecenter than in the outer regions, and thereby approximate the gate width8-1 of the chip in the center portion to the gate width 8-2 in the chipin the outer regions. In this case, it is possible to introduce aprocessing gas with higher oxygen concentration from the second gasinlets 65-2 placed in the outer regions than from the first gas inlet65-1 placed in the center of the processing chamber cover 12. Theanalysis section 74 calculates the necessary flow rate ratios, flowrates and processing pressures of the respective processing gasesintroduced through the first and second gas inlets 65 to realize thiscondition. That is, the set flow rate values of the flow rate regulators42-1, 42-2, 53-1 and 53-2, the set shunt ratio values of the gas shunt60 and set value of the opening of the pressure regulating valve 31 torealize the set processing pressure are calculated.

The above described analysis is performed by the analysis section 74,the control command 75 reflecting the analysis result is sent to thecontrol section 76 and the control signal 77 is sent from the controlsection 76 to the devices of the gas piping system. That is, the controlsignal 77 including the set flow rate value is sent to the respectiveflow rate regulators 42-1, 42-2, 53-1 and 53-2, valve ON/OFF controlsignal 77 is sent to the respective valves 43-1, 43-2, 54-1 and 54-2,the control signal 77 including the set shunt ratio value is sent to thegas shunt 60 and the control signal 77 including the set value of theopening to realize the set processing pressure is sent to the pressureregulating valve 31.

As shown above, based on the measurement result of the photoresist maskwidth 7 obtained by the measuring instrument 70, it is possible toapproximate the gate width 8-1 of the chip in the center of the objectto be processed 1 to the gate width 8-2 of the chip in the outerregions.

Next, a case where the gate width 8 of the object to be processed 1 ismeasured after etching will be explained. First, the gate width 8 ismeasured at a plurality of locations on the surface of the object to beprocessed 1 using measuring instrument 70 such as a CD-SEM, OCDmeasuring instrument or AFM, and the measured data 71 is sent to thedatabase 72. This measured data 71 includes data indicating themeasurement locations in the object to be processed 1, and data of thegate width 8 after etching. Furthermore, when a plurality of objects tobe processed is processed continuously in mass production, the measureddata 71 also includes data for identifying data of each of the pluralityof objects to be processed. As with the measurement of the photoresistmask width 7, the gate width 8 is measured at the same locations in aplurality of chips formed on the surface of the object to be processed1, and an in-plane distribution of the object to be processed 1 of thegate width 8 is calculated.

The data 73 stored in the database 72 is sent to the analysis section 74at appropriate timings. The analysis section 74 analyzes the in-planedistribution of the gate width 8 on the surface of the object to beprocessed 1 based on the data 73. For example, when the gate width 8-1of the chip in the center portion of the object to be processed 1 islarger than the target completion size and the gate width 8-2 of thechip in the outer regions is smaller than the target completion size, byregulating the gas condition so that the gate width 8-1 becomes smallerin the chip in the center portion and the gate width 8-2 becomes largerin the chip in the outer regions, it is possible to approximate the gatewidth 8-1 of the chip in the center portion and the gate width 8-2 ofthe chip in the outer regions to the target completion size of the gatewidth 8. In this case, it is possible to reduce the oxygen concentrationof the processing gas 21-1 introduced through the first gas inlet 65-1placed in the center of the processing chamber cover 12 and increase theoxygen concentration of the processing gas 21-2 introduced through thesecond gas inlet 65-2 placed in the outer regions. The flow rate ratios,flow rates and processing pressures of the processing gases introducedthrough the first and second gas inlets 65 necessary to realize thiscondition are calculated by the analysis section 74. That is, the setflow rate values of the flow rate regulators 42-1, 42-2, 53-1 and 53-2,the shunt ratio set value of the gas shunt 60 and the set value of theopening of the pressure regulating valve 31 to realize the setprocessing pressure are calculated.

The above described analysis is performed by the analysis section 74,the control command 75 reflecting the analysis result is sent to thecontrol section 76 and the control signal 77 is sent from the controlsection 76 to the devices of the gas piping system. That is, the controlsignal 77 including the set flow rate value is sent to the respectiveflow rate regulators 42-1, 42-2, 53-1 and 53-2, valve ON/OFF controlsignal 77 is sent to the respective valves 43-1, 43-2, 54-1 and 54-2,the control signal 77 including the shunt ratio set value is sent to thegas shunt 60, and the control signal 77 including the set value of theopening to realize the set processing pressure is sent to the pressureregulating valve 31.

As shown above, through feedback control of the etching processingcondition based on the measurement result of the gate width 8 obtainedby the measuring instrument 70, it is possible to approximate the gatewidth 8-1 of the chip in the center portion of the object to beprocessed 1 and the gate width 8-2 of the chip in the outer regions tothe target completion size.

The target of the feedback control applied to the etching processingcondition based on the measurement result of the gate width 8 may alsobe a processing of another object to be processed carried outimmediately after the measurement of the object to be processed or maybe processing of the object to be processed carried out after aprocessing of two or more objects. Furthermore, a group of objects to beprocessed are handled in a unit called a “lot” in mass production, andthe aforementioned feedback control target may also be a processingcarried out one lot or more after the processing of the measured objectto be processed. Since measurement using the measuring instrument 70 maytake a long time, it is also possible to carry out feedback control onthe processing carried out 1 lot or more after the processing of themeasured object to be processed based on the measurement result.Furthermore, when processing for manufacturing multiple types ofelectronic devices is carried out using the same plasma etchingapparatus, processing conditions which vary from one type of product toanother are often used. For this reason, the target of feedback controlis preferably the processing of electronic devices of the same type.

This embodiment uses the processing chamber 13 having the gas inlets 65formed in the processing chamber cover 12 as shown in the firstembodiment, but the present invention is not limited to this embodiment.It is also possible to use the processing chamber 13 using theshowerhead plate 19 as shown in the second embodiment.

Fourth Embodiment

The fourth embodiment of the present invention will now be explainedwith reference to FIG. 11. This embodiment adds a photoreception window80, an optical fiber 81, a spectroscopic section 82, a database 72, ananalysis section 74 and a control section 76 to the structure explainedin the first embodiment that allows processing gases with different flowrates and compositions to be introduced through a plurality of gasinlets 65.

The photoreception window 80 is provided in a processing chamber wall 11to allow emission of plasma 25 to be received, and the plasma emissionreceived by the photoreception window 80 is guided to the spectroscopicsection 82 through the optical fiber 81. The plasma light is dispersedinto a spectrum at the spectroscopic section 82, further converted tomulti-channel signals (e.g., signals of 1024 channels in a wavelengthrange of 200 nm to 800 nm in this embodiment) at certain samplingintervals (e.g., 1 second) periodically every certain wavelength by aCCD (charge-coupled device) incorporated in the spectroscopic section82. Plasma emission data 83 consisting of multi-channel signals is sentto the database 72. Data 73 stored in the database 72 is sent to theanalysis section 74 at appropriate timings, and the analysis section 74analyzes the plasma 25 from the data 73.

When etching process is performed as described above, reaction productsare deposited on the inner surfaces of the processing chamber side wall11 and processing chamber cover 12. This deposition is also deposited onthe inner side of the photoreception window 80, which causes a reductionin the amount of photoreception of the plasma 25 by the optical fiber81. If the composition and film quality of the deposition on the innerside of the photoreception window 80 are the same, the reduction in theamount of photoreception increases as the thickness of the depositionincreases. Furthermore, the reduction in the amount of photoreception ateach wavelength varies depending on the wavelength. On the other hand,as shown above, the reaction products deposited on the inner sides ofthe processing chamber side wall 11 and processing chamber cover 12 aredissociated by the plasma 25, producing ions of silicon and bromine,etc., which may affect the etching of the object to be processed 1 andprovoke a variation of the gate width 8. Thus, there is a correlationbetween the amount of photoreception of the plasma 25 at each wavelengthand variation in the gate width 8.

This embodiment calculates in advance a polynomial showing arelationship between the data 73 indicating plasma emission and the gatewidth 8, and carries out an analysis through the analysis section 74using this polynomial. Assuming that the gate width 8 at the chip in thecenter portion of the object to be processed 1 is Gc and the i-thchannel signal of the multi-channel signals obtained through thespectroscopic section 82 is Ii, Gc and signal I of each channel areexpressed by the following Formula (1) where f₁ indicates that Gc is afunction of I.[Formula 1]Gc=f ₁(I ₁ ,I ₂ , . . . , I ₁₀₂₄)  (1)

Likewise, assuming that the gate width 8 at the chip in the outerregions of the object to be processed 1 is Go and the i-th channelsignal of the multi-channel signals obtained through the spectroscopicsection 82 is Ii, Go and signal I of each channel are expressed by thefollowing Formula (2) where f₂ indicates that Go is a function of I.[Formula 2]Go=f ₁(I ₁ ,I ₂ , . . . , I ₁₀₂₄)  (2)

According to these polynomials, the gate width 8 of the chips in thecenter portion and outer region of the object to be processed 1 iscalculated and its in-plane distribution is analyzed. For example, ifthe analysis result shows that the gate width 8 at the chip in thecentral part of the object to be processed 1 is larger than a targetcompletion size and the gate width 8 at the chip in the outer region issmaller than the target completion size, by regulating the gas conditionso that the gate width 8 at the chip in the center portion becomessmaller and the gate width 8 at the chip in the outer region becomesgreater, it is possible to approximate the gate widths 8 at the chips inthe center portion and in the outer region to the target completionsize. In this case, it is possible to reduce the oxygen concentration ofthe processing gas 21-1 introduced from the first gas inlet 65-1 placedin the center of the processing chamber cover 12 and increase the oxygenconcentration of the processing gas 21-2 introduced from the second gasinlet 65-2 placed in the outer region. It is possible to improve thein-plane distribution of the gate width 8 of the object to be processed1 and approximate it to the target completion size using these analysisresults and by carrying out control similar to that in the thirdembodiment.

As shown above, by controlling the etching processing condition in realtime based on the light emission measurement result of the plasma 25obtained by the spectroscopic section 82, it is possible to approximatethe gate width 8-1 in the center portion and the gate width 8-2 in theouter regions of the object to be processed 1 to their respective targetcompletion sizes.

Here, multi-channel signals obtained by the spectroscopic section 82 areused as variables making up the f₁ or f₂ function used to calculate thegate width 8, but the number of channels is not particularly limited.This embodiment uses signals I of all 1024 channels, but it is alsopossible to use signals I of several channels or one channel out of themulti-channel signals obtained.

Fifth Embodiment

A fifth embodiment of the present invention will be explained using FIG.12. This embodiment adds one additional set of photoreception window 80and optical fiber 81 to the configuration explained in the fourthembodiment. It also provides two photoreception windows 80 in the centerportion and outer regions of the processing chamber cover 12, analyzesconcentrations of radicals and ions in the center portion and outerregions in the processing chamber 13 to regulate flow rates andcompositions of processing gases 21 introduced from a plurality oflocations. A specific method of implementing this embodiment will beexplained below.

To allow reception of emission of plasma 25, a first photoreceptionwindow 80-1 is provided in the center portion of the processing chambercover 12 and a second photoreception window 80-2 is provided in theouter regions. Emissions of the plasma 25 received by the respectivephotoreception windows 80 are guided to a spectroscopic section 82through an optical fiber 81-1 and an optical fiber 81-2. The respectiveplasma emissions are dispersed into a spectrum at the spectroscopicsection 82, further converted to multi-channel signals (e.g., signals of1024 channels in a wavelength range of 200 nm to 800 nm in thisembodiment) at certain sampling intervals (e.g., 1 second) periodicallyevery certain wavelength by a CCD incorporated in the spectroscopicsection 82. Plasma emission data 83 consisting of multi-channel signalsis sent to a database 72. Data 73 stored in the database 72 is sent toan analysis section 74 at appropriate timings, and the analysis section74 analyzes the plasma 25 based on the data 73.

Ions and radicals in the plasma 25 emit light having a wavelengthspecific to each component. For example, 288 nm or the like for Si, 827nm or the like for Br, 617 nm or the like for O and 503.5 nm or the likefor SiBr. Thus, by analyzing the plasma emission data 83 obtained fromthe first photoreception window 80-1 placed in the center portion andthe second photoreception window 80-2 placed in the outer regions of theprocessing chamber cover 12, it is possible to compare concentrations ofions and radicals in the center portion and outer regions of the objectto be processed 1.

Thus, if an analysis result shows that, for example, the SiBrconcentration in the center portion is relatively similar to that in theouter regions and the O concentration is lower in the outer regions thanin the center portion, it is possible to introduce a processing gas 21-2with higher oxygen concentration from the second gas inlet 65-2 placedin the outer regions rather than the processing gas 21-1 introduced fromthe first gas inlet 65-1 placed in the center portion of the processingchamber cover 12. As a result, it is possible to control theconcentration distribution of oxygen in the processing chamber 13uniformly and approximate the gate width 8 at the chip in the centerportion of the object to be processed 1 to the gate width 8 at the chipin the outer regions. The analysis section 74 calculates the flow rateratios, flow rates and processing pressures of the respective processinggases introduced from the first and second gas inlets 65 necessary torealize this condition. That is, the set flow rate values of the flowrate regulators 42-1, 42-2, 53-1 and 53-2, set shunt ratio value of thegas shunt 60 and set value of the opening of the pressure regulatingvalve 31 to realize the set processing pressure are calculated.

The above described analysis is performed by the analysis section 74,the control command 75 reflecting the analysis result is sent to thecontrol section 76 and the control signal 77 is sent to the devices ofthe gas piping system from the control section 76. That is, the controlsignal 77 including the set flow rate value is sent to the respectiveflow rate regulators 42-1, 42-2, 53-1 and 53-2, the valve ON/OFF controlsignal 77 is sent to the respective valves 43-1, 43-2, 54-1 and 54-2,the control signal 77 including the set shunt ratio value is sent to thegas shunt 60 and the control signal 77 including the set value of theopening of the valve to realize the set processing pressure is sent tothe pressure regulating valve 31.

As shown above, by controlling the etching processing condition in realtime based on emissions of the plasma 25 received through the firstphotoreception window 80-1 placed in the center portion of theprocessing chamber cover 12 and the second photoreception window 80-2placed in the outer regions, it is possible to approximate the gatewidth 8 at the chip in the center portion of the object to be processed1 to the gate width 8 of the chip in the outer regions and improve thein-plane uniformity of the gate width 8.

The embodiments of the present invention have been explained using gateetching as an example, but application of the present invention is notlimited to gate etching. It goes without saying that the presentinvention is also applicable to a plasma etching apparatus and plasmaetching method targeted at metal such as aluminum (Al), or silicondioxide (SiO₂) and ferroelectric material or the like.

As described above, the present invention provides a plasma etchingprocessing apparatus and plasma etching processing method which performprocessing with excellent in-plane uniformity on an object to beprocessed having a large diameter.

1. A plasma etching method for a plasma etching apparatus comprising: aprocessing chamber for performing plasma etching on an object to beprocessed; a plurality of gas supply sources for supplying processinggases to the processing chamber; a gas shunt for dividing the processinggas from the gas supply source; a first gas inlet for introducing afirst processing gas flow divided by the gas shunt to the object to beprocessed via a center portion of a top of the processing chamber; asecond gas inlet provided separately from the first gas inlet and placedon an outer side of the first gas inlet for introducing a secondprocessing gas flow divided by the gas shunt to the object to beprocessed via an outer region of the top of the processing chamber; athird processing gas supply means for supplying a third processing gasto at least one of the divided gas pipes of the first processing gasflow and the second processing gas flow; a plurality of flow rateregulators for regulating flow rates of the processing gases; a firstphotoreception section disposed at a top of the processing chamber forreceiving plasma emission light from a center portion of the processingchamber; a second photoreception section disposed at the outer side atthe top of the processing chamber and provided separately from the firstphotoreception section, the second photoreception section receivingplasma emission light from the processing chamber at a differentlocation from the first photoreception section; a spectroscopic sectionfor discomposing the plasma emission light into a plurality ofwavelength components, where the plasma emission light is received atthe first and the second photoreception sections and is in theprocessing chamber; an analysis section for analyzing eachconcentrations of a plurality of radicals in the plasma based on thewavelength components discomposed in the spectroscopic section; and acontrol unit for supplying the third processing gas to at least one ofthe gas pipes of the first processing gas flow and the second processinggas flow based on an analysis result in the analysis section, andcontrolling the introduction of processing gases having differentcompositions from the first gas inlet and the second gas inlet in orderto control distribution of depositional reaction products; the methodcomprising: a first photoreception step for receiving light from acenter portion of the processing chamber; a second photoreception stepfor receiving light from the processing chamber at a different locationfrom the first photoreception section receiving light from the centerportion of the processing chamber; a spectroscopic step for discomposingthe plasma emission light into a plurality of wavelength components; astep for performing analysis based on the data obtained in thespectroscopic step and generating a control instruction for controllingthe flow rate of the flow rate regulator, for controlling a flowdividing ratio of the gas shunt, and for controlling the processing gassupply quantity of the third processing gas supply means; and a controlstep for generating a control signal based on the control instruction;wherein the third processing gas is supplied to at least one of the gaspipes of the first processing gas flow and the second processing gasflow, and processing gases having different compositions are introducedfrom the first gas inlet and the second gas inlet in order to controlthe distribution of depositional reaction products.
 2. A plasma etchingmethod for a plasma etching apparatus comprising: a processing chamberfor performing plasma etching on an object to be processed; a first gassupply source for supplying a processing gas to the processing chamber;a second gas supply source provided separately from the first gas supplysource for supplying processing gas to the processing chamber; a gasjunction where the processing gases from the first and second gas supplysources are merged; a gas shunt for dividing the merged processing gasfrom the gas junction; a first gas inlet for introducing a firstprocessing gas flow divided by the gas shunt to the object to beprocessed via a center portion of a top of the processing chamber; asecond gas inlet provided separately from the first gas inlet and placedon an outer side of the first gas inlet at the top of the processingchamber for introducing a second processing gas flow divided by the gasshunt to the object to be processed via the top of the processingchamber; a third gas supply means for supplying a third processing gasto at least one of the divided gas pipes of the first processing gasflow and the second processing gas flow; a plurality of flow rateregulators for regulating flow rates of the first, second and thirdprocessing gases respectively; a first photoreception section disposedat a top of the processing chamber for receiving plasma emission lightfrom a center portion of the processing chamber; a second photoreceptionsection disposed at the outer side at the top of the processing chamberand provided separately from the first photoreception section, thesecond photoreception section receiving plasma emission light from theprocessing chamber at a different location from the first photoreceptionsection; a spectroscopic section for discomposing the plasma emissionlight received at the first and the second photoreception sections andis in the processing chamber into a plurality of wavelength components;a database for storing a spectroscopic result of the spectroscopicsection; an analysis section for analyzing each concentrations of aplurality of radicals in the plasma based on the wavelength componentsdiscomposed in the spectroscopic section and the data stored in thedatabase; and a control unit for generating a control signal based on ananalysis result in the analysis section and a control instruction,supplying the third gas to a gas pipe between the gas shunt and at leastone of the gas inlets of the first processing gas and the secondprocessing gas based on the control signal, and controlling theintroduction of processing gases having different compositions from thefirst gas inlet and the second gas inlet in order to controldistribution of depositional reaction products; the plasma etchingmethod comprising; a first photoreception step for receiving light froma center portion of the processing chamber; a second photoreception stepfor receiving light from the processing chamber at a different locationfrom the first photoreception section for receiving light from thecenter portion of the processing chamber; a spectroscopic step fordiscomposing the plasma emission light into a plurality of wavelengthcomponents; a step for storing a result obtained in the spectroscopicstep; an analyzing step for analyzing each concentrations of a pluralityof radicals in the plasma based on the data stored in the storing stepand the data stored in the database in order to generate a controlinstruction; a control step for generating a control signal based on thecontrol instruction; wherein the third processing gas is supplied to atleast one of the gas pipes of the first processing gas flow and thesecond processing gas flow, and processing gases having differentcompositions are introduced from the first gas inlet and the second gasinlet in order to control the distribution of depositional reactionproducts.